1. Field of the Invention
The invention relates to the field of earth boring tools and more particularly to methodologies for transmitting tool face orientation data within a bore hole.
2. Description of the Prior Art
In order to successfully operate a directional drill it is necessary to know the orientation of the drill bit downhole at all times. The orientation, or angular position of the tool face downhole is sensed by a downhole mechanism, such as gravitational or magnetic sensors and then transmitted to the well platform where the directional drilling procedure is controlled. Transmission is typically through mud pulsing which is relatively slow, particularly compared to electronic communication rates, so that there is a premium placed upon efficiency of the downhole communication technique. In one prior art tool, borehole orientation is communicated uphole in forty-eight bits of information transmitted in straight serial binary form at one second intervals, LICHTE, Jr. et al., "Borehole Orientation Tool", U.S. Pat. 3,771,118 (1973).
The tool face orientation is generally described in angular coordinates, such as borehole inclination and azimuth. Therefore, a plurality of parameters must be transmitted in order to obtain a complete characterization of tool orientation. See, for example, ARMISTEAD, "Borehole Directional Logging", U.S. Pat. No. 3,691,363 (1972).
Therefore, what is needed is a transmission protocol whereby tool face orientation may be efficiently transmitted to the well surface in a manner which is not subject to the defects of the pior art, and which may be transmitted in reduced time.